Chinese ship Shen Neng 1 ran aground in the Great Barrier Reef late Saturday, leaking oil into the world's largest reef system. According to WWF Australia, the reef has 1,500 species of fish, 359 types of hard coral, one third of the world's soft corals, 175 bird species, six of the world's seven species of threatened marine turtle, more than 30 species of marine mammals, 5,000 to 8,000 molluscs and thousands of different sponges, worms, crustaceans, 800 species of echinoderms and 215 bird species.

With so much at stake, many are concerned over how much damage the ship's presence could inflict on the pristine, rich environment, with experts predicting it could take weeks to clean up the mess. The incident highlights just how fragile the massive reef is to foreign invaders, whether they be humans, invasive species, or even sediment. As part of Our Oceans week, we're taking a look at the biggest threats facing the Great Barrier Reef. What do you think is the biggest potential danger to the world's largest reef system?

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The Biggest Threats Facing The Great Barrier Reef

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The recent Chinese shipping disaster in the reef underscores the damage human presence can have on such a delicate environment that is so hugely reliant on its reef system. The Shen Neng 1 ran aground when it was taking a shortcut through the reef, leaking oil into the waters. It's now dangerously close to breaking apart, which could result in the leakage of its 1,000 tons of heavy fuel oil. Many are now calling foul on using such a pristine environment as a "coal highway" for bulk carriers. According to the Great Barrier Reef Marine Park Authority, 282 confirmed vessel spills were recorded in the Great Barrier Reef World Heritage Area between 1987 and 2002.

The biggest impact a warming climate has on the Great Barrier Reef is the damage it does to the coral reefs. Rising sea temperatures lead to coral bleaching, which is the whitening of corals that can eventually kill the coral, or at least make it difficult for them to reproduce. The most intense instances of coral bleaching occurred in 1998 and 2002, when raised temperatures left almost 60% of reefs at least somewhat bleached.
Charlie Veron, former chief scientist of the Australian Institute of Marine Science, told The Times last year that once carbon dioxide reaches the levels predicted for 20 years from now, coral reefs will be doomed to extinction. Veron said: “They would be the world’s first global ecosystem to collapse. I have the backing of every coral reef scientist, every research organisation. I’ve spoken to them all. This is critical. This is reality.”

The fishing industry makes up a large part of Australia's economy, but it can take a toll on the reef's ecosystem. Bottom trawling can destroy habitats and result in bycatch, which is the unintentional catching of animals, such as turtles and dolphins. Overfishing of species near coral reefs, especially vital herbivores, has put the reef ecosystem into disarray.

80% of the land adjacent to the Great Barrier Reef is farmland that supports agricultural production, which poses a threat to the reef. The fertilizers used can run off into groundwater and surface water if the farmers overfeed, thereby polluting the waters. Pesticides are also found in runoff when the farm soil erodes, taking the chemicals downstream and into the reef.

The amount of sediment running from the land into the Great Barrier Reef has quadrupled over the past 150 years, due largely to grazing and cropping expansion. Sediment runoff can destroy coral reefs by stifling when particles settle out, reducing light and potentially reducing photosynthesis and growth.

Ballast water is water contained in ships, sometimes with sediments, to stabilize them while in transit. Hull fouling is when organisms attach themselves to the hull of a ship during a voyage. The number of foreign marine species introduced to Australian waters through ballast water discharges and ship hull fouling is estimated at more than 250 different species. The species that arrive from Southern Japanese ports and ports in Singapore and Taiwan can pose a threat because the species come from warmer waters and are more likely to alter the Great Barrier Reef ecosystem.